The present invention relates to methods of making shaped structures with an overcoat layer. The present invention also relates to making polymeric structures such as cannulas and catheters. In addition, the present invention also relates to urinary catheters and most particularly to female urinary catheters.
Many structures, for example, hoses, condoms, gloves, cannulas, catheters, and the like, are made of a polymeric material (e.g., latex, silicone). Such polymeric structures may have various shapes, e.g., sections with different diameters, contours, etc. In addition, various cavities might be present in the structures, some of which might contain fluids of various types. A traditional way to form such structures is by adhesively affixing parts together so that the outer coat can attain the desired shape. However, these traditional methods do not lend themselves to mass production and are labor intensive. Some shapes are extremely difficult if not impossible to make by traditional adhesive methods. Likewise, traditional methods of making shaped structures of nonpolymeric substances, such as inorganic materials, with cavities therein sometimes have similar difficulties.
An example of a shaped polymeric structure is a catheter. Most catheters are cannulas or tube like devices which are inserted into a portion of a person""s body in order to transport fluids, such as liquids, gases, and sometimes semisolid material, in or out of that particular portion of the body. For instances, urinary catheters are used to transport urine collected in the bladder out of the body via the urinary tract. Other types of catheters such as gastronomy devices, transport fluids into and out of various segments of the gastrointestinal system, primarily the stomach.
In order to provide a means of retaining the catheter within the body, inflatable bag catheters were introduced many years ago. Subsequently, Foley (U.S. Pat. No. 3,409,016) taught an elongated catheter having a secondary lumen for inflating a retention balloon at a distal end of the catheter once the distal end is positioned within the body. Generally, the xe2x80x9cdistal endxe2x80x9d is the end of the catheter that is first introduced into the body when the catheter is being positioned within the body and the xe2x80x9cproximal endxe2x80x9d is the end opposite the distal end. Such catheters are now generally referred to as xe2x80x9cFoleyxe2x80x9d catheters out of respect for the contribution made by Dr. Foley. Because of the variation in needs of patients, improvements on Dr. Foley""s contribution to the catheter art are continually being made. These improvements sometimes result in cannulas or catheters that have shapes quite different from that of the device originally designed by Dr. Foley.
Traditionally, Foley catheters are made by a process which includes slipping a band of cured rubber over a double lumen latex rubber tubing and affixing the band on the double lumen tubing by dipping the band and the tubing in a suspension of latex to form an outer layer. The cost of manufacturing traditional Foley catheters has been influenced by the need to use a significant amount of hand labor to make the devices, especially the silicone rubber Foley catheters. Moreover, in many cases where a polymeric structure such as a catheter is to have a cavity filled with fluid, traditional manufacturing methods can not be used. It will be appreciated that using such traditional methods to make catheters that have a variety of shapes and sizes of cavities between the tubing and the outer layer would add significantly to the cost of production and pose limitations on the variety of catheters that can be made. Reducing the amount of hand labor in the manufacture of such devices may reduce the cost of such devices so as to provide a more affordable product to the consumer and to render such a product more competitive in the market place.
The same problem of high labor cost and limitation of the variety of shapes is similarly encountered in the manufacture of other shaped structures such as gastronomy devices, condom, and hoses. The present invention provides a method of making polymeric structures which offers substantial advantages over traditional manufacturing methods. In addition, the present invention provides a simple, easily applied, comfortable disposable catheter for incontinent females.
The present invention relates to making a shaped structure by coating at least a portion of a shaped structure of a bond-preventing agent with a liquid composition, e.g. a polymeric bonding composition such as one that contains uncured silicone rubber, to attain an overcoat layer of a desired shape. The shaped structure of a bond-preventing agent can be formed by coating over an outer surface of a support structure, for example, a mandrel or a tube, to form a residual coating of a particular shape.
One embodiment of the present invention relates to dipping a mandrel in a liquid composition, such as polymeric composition to form an inner piece (or structure) over a surface of a mandrel, applying and shaping a residual coating of a bond-preventing agent over the outer surface of the inner piece, and coating at least a portion of the structure resulting from the previous steps with a liquid composition to form a shaped structure having an overcoat on an inner piece.
Another embodiment of the present invention relates to a method of making a polymeric structure in accordance with one of the above methods wherein a fluid-filled cavity is formed between an inner polymeric layer and an outer polymeric layer.
Yet another embodiment of the present invention relates to a method of making a polymeric structure in accordance with one of the above methods wherein an outer polymeric layer only partially encapsulates an inner polymeric layer such that only one end of the outer polymeric layer is attached to the polymeric structure. This method might be utilized to form a polymeric structure having an umbrella-like structure.
It will be appreciated that shaped structures of varying shapes can be formed by the present invention. The shaped structures formed by the present invention might be hollow, liquid-filled, gel-filled, etc. and/or might include a solid piece as well as combinations thereof.
The coating of the bond-preventing agent can have a varying thickness on different portions of an outer surface of the inner piece. The coating of the bond-preventing agent remaining on the inner piece before the coating of the liquid composition is herein referred to as the xe2x80x9cresidual coating.xe2x80x9d The shape of the overcoat layer results from the varying thicknesses of the residual coating of the bond-preventing agent.
In one embodiment, the forming of residual coating of varying shapes can be done by coating portions of an outer surface of the inner piece with a bond-preventing agent in a plurality of dipping steps by immersing the inner piece into the bond-preventing agent to a desired depth for a desired length of time and subsequently removing the inner piece from the bond-preventing agent. The desired depth and the desired length of time for each of the plurality of dipping steps is selected so that a residual coating of bond-preventing agent of desired thickness and shape remains on portions of the inner piece following the plurality of dipping steps. The residual coating has a specific shape as a result of the variation between the depth of any two of the plurality of dipping steps, the number of dipping steps, the length of time between any two of the plurality of dipping steps, and the varying speeds of withdrawal from the liquids in dip tanks. By appropriate coating and stripping sequence, the bond-preventing agent can be sculpted to result in desired, symmetrical shapes much as the shapes achievable using a lathe. The sculpted residual coating can have varying thickness, curves, and angles, and therefore a specific, desired shape. By subsequently coating the residual coating of bond-preventing agent, which coats the inner piece, with a polymeric bonding composition, a shaped overcoat layer is formed wherein the shape of the overcoat layer results from the varying shapes of the residual coating. Also, other shaped structures, such as a bullet-shaped, molded, solid polymeric tip can be added to the inner piece before the formation of the overcoat layer to attain a desirable shape for a particular part of the shaped structure with the polymeric overcoat. As used herein, two structures of similar shapes but having unequal ratios of dimensions in the two structures are considered to have different shapes. For example, annular cylinders with the same inside diameter and length but different outside diameters are not considered to have the same shape. As used herein, the residual coating is still considered xe2x80x9ca residual coatingxe2x80x9d even if it is not continuous over two or more portions of the inner piece as long as the coating is not radially separated into layers by a different intervening substance.
In one embodiment, the step of coating the inner piece with the bond-preventing agent can include a step of stripping the inner piece by immersing the inner piece in a stripping fluid to a desired depth for a desired length of time following any of the plurality of dipping steps in order to remove at least a portion of the bond-preventing agent from the outer surface of the inner piece. After the stripping step, the inner piece can be dipped into the bond-preventing agent again to form another coat of the bond-preventing agent on a selected portion of the inner piece if desired. The portion of the inner piece that has been stripped can be dipped in a bond-preventing agent to form a coating. If desired, to form a particular shape, both the stripped portion of the inner piece and a portion of the bond-preventing agent coating that remains on the inner piece can be dipped into the bond-preventing agent. The thickness of the bond-preventing agent coating can be increased by repeating the dipping and removal steps.
In one embodiment the inner piece might be a simple cylindrical mandrel. Such a mandrel can be used for making, for example, a polymeric hose or tube. In another embodiment, the inner piece can be a polymeric tube. Such a polymeric tube can either be purchased or formed by a process that comprises dipping a mandrel in a polymeric bonding composition. Such a polymeric tube typically can have a closed tip at one end.
In an alternate embodiment, a method of mass producing polymeric structures is provided. This method comprises providing a plurality of mandrels, each mandrel having the aforementioned elements; coating portions of an outer surface of the mandrel with a bond-preventing agent in a plurality of dipping steps by immersing the mandrel into the bond-preventing agent to a desired depth for a desired length of time and removing therefrom, stripping portions of the bond-preventing agent by dipping in a stripping agent, and alternately dipping and stripping to achieve the desired shape, and then coating the mandrel, now at least partially coated with the bond-preventing agent, with a polymeric bonding composition to form a shaped overcoat layer.
The present invention enables the production of structures, such as polymeric structures, with a great reduction of hand labor, which not only is costly, but also contribute to inconsistent results. The present invention can be adapted to produce structures of a wide variety of sizes and shapes by varying the thickness of the residual coating of the bond-preventing agent. The variation of the thickness of the residual coating of the bond-preventing agent can be designed to result in a structure with an overcoat of a specific shape. Because of the variation of need for different types of structures, e.g., simple Foley balloon catheters for placement in the urinary tract, balloon catheters with cavities containing bactericidal agents, catheters with cylindrical sleeve with a lubricant, and the like, a variety of shapes are needed for such structures.
The present invention also provides the advantage of obviating the need to machine a solid (such as metallic) mandrel of a specific shape for making a structure with overcoat of that specific shape. Moreover, often such mandrels cannot be used to make overcoat layers of complex shapes. For example, once a polymeric overcoat layer is formed on a mandrel with a shape as that of the inner tube and the coating of bond-preventing agent shown in FIG. 11A, it is very difficult to remove the overcoat layer from the mandrel. Although injection molding using very expensive cavity molds may be used to make structures with overcoat layers, the resulting overcoat layer has xe2x80x9cpart linesxe2x80x9d where the mold is opened to allow removal of the molded structure. Such shortcomings can be overcome by using the method of the present invention.
In the making of polymeric structures using the method of the present invention, the outside dimensions (e.g. diameter) can be made with more consistency than in similar products made by traditional manufacturing methods, such as affixing balloon portions to the outer surface of a tube by hand. The method of the present invention makes possible the highly automated process of fabricating polymeric structures with shaped gel-filled, liquid filled cavities, especially those with a soft, outer, elastomeric layer that can conform to the contour of a surface in contact therewith.
The present invention further relates to a female catheter having an inner tube and an outer layer encircling the tube. In an embodiment of a female catheter of the present invention, a cavity is interposed between the tube and overcoat layer. A fluid is contained in the cavity. The cavity is enlarged at two spaced apart locations along the inner tube so as to form a balloon portion and a reservoir portion connected by a sleeve section. The sleeve portion is in fluid communication with the balloon and reservoir portions such that fluid is capable of flowing between these portions whereby the size of the balloon and reservoir portions can vary depending on the amount of fluid in each of the portions. The reservoir portion at a proximal end of the catheter is normally in an enlarged state although it is readily compressible into a compressed state. The overcoat has reservoir, sleeve, and balloon sections corresponding to the respective portions of the cavity.
In one embodiment of the invention, a collar encircles the sleeve section of the overcoat to restrict fluid flow between the various portions of the cavity through the sleeve portion and a shroud encircles the reservoir section of the overcoat to limit lateral ballooning thereof when the reservoir section is compressed by forces not completely enveloping the reservoir section.
In another embodiment of the invention, a female catheter as described above further includes a removable stiff plastic stylet inserted into the inner tube to facilitate insertion of the catheter.
The present invention provides a simple, comfortable, disposable female catheter which can be manually inserted by incontinent females and is hand-actuated to achieve retention in a body passageway.
In using one embodiment of the present invention, a distal end of the catheter is inserted into the urethral tract by exerting force on the stylet. Upon emergence into the bladder of the first balloon section at the distal end of the catheter, the fluid in the reservoir portion of the cavity can be forced through the sleeve portion into the balloon portion by compressing the reservoir section of the overcoat layer to inflate the balloon section, thus retaining the catheter in the body passageway. The sleeve section of the catheter can be made to conform to the urethral tract walls providing a leak proof fit. It will be appreciated, that the catheter can allow the inner drain tube to twist and move within the soft outer layer. An elastomeric shroud encircles the reservoir section of the overcoat to limit the lateral ballooning thereof. An elastomeric collar restricts the sleeve section to prevents fluid from being forced back from the balloon portion to the reservoir portion of the cavity during normal activities of the user.
This catheter has the advantage that a limited amount of fluid is confined in the cavity, and therefore the balloon cannot be overinflated. The utilization of a stylet facilitates the insertion of the catheter. The length of the catheter can be designed such that as the reservoir section of the catheter is proximate the outside entrance of the urethra, the balloon section is disposed in the bladder proximate the entrance to the urethra effective to prevent fluid communication between the urethra and the bladder. The catheter can be made with soft material. Because the overcoat layer of the catheter gently conforms to the urethral wall, irritation to the body tissue is greatly reduced, thus lowering the risk of infection. Further, when the catheter is to be withdrawn, the restriction on the sleeve section can be easily removed by pulling the shroud and the collar from the catheter. Therefore, the retention catheter can be easily inserted, positioned, and withdrawn by the patient without the aid of a health professional.
In one embodiment, the fluid in the catheter is mineral oil. The mineral oil migrates to an outer surface of a silicone rubber outer layer to provide a lubricated, low friction surface.
The present invention, its advantages and other objects obtained by its use are also illustrated by the drawings, and the accompanying descriptive material, in which the preferred embodiments of the present invention are described.